@All, Thanks for the input.
To make it a bit more clear, basically I'd be paying about $49k in 2012 for 120 credit hours of education at a Florida University in roughly 2030. The 3.95% interest is interest applied (meaning I pay it, not get it) if I spread the payments over 18 years-- thus the 18 year plan ultimately costs $64k, as indicated in the OP.
@dragoncar, 2011 tuition rates put 120 hours at $22,626 (~$189/hr). About $5700/year ish. So, I'd be paying more than twice that (~$406/hr). For comparison though, 18 years ago (1993), the rate was $57/hr ($90/hr, in 2011 dollars adjusted for inflation).
The past few years have had particularly dramatic jumps in tuition. In 2007 the rate was $109/hr ($119 in 2011 dollars)-- so it's nearly doubled during this recent period of economic difficulty.
Part of what I'm struggling with is that if I pay lump sum, I'm overpaying in 2011 dollars for a service in provided in 2030. In 2030 the tuition rate will have been impacted by both inflation and the rise (or decline) in college tuition beyond inflation. Is there a benefit to spreading the payments out over 55 months, or 18 years?
If we assume inflation will have a positive value each year for the next 18 years then the lump sum payment pays the entire amount with the most valuable dollars.